Diagnostics Flashcards
(37 cards)
What are the possible complications of lumbar puncture? Give at least 3.
(1) Headache, especially in patients with migraine
(2) bleeding into the spinal/ epidural space
(3) infection, if technique is not sterile
What blood parameters can signify increased risk of bleeding into the spinal/epidural space in patients who are about to undergo lumbar puncture?
(1) patients on anticoagulation, with INR greater than 1.4
(2) patients with low platelet counts ( less than 50,000/ mm3)
(3) patients with impaired platelet function (as in alcoholism or uremia)
What is the normal CSF pressure in an adult in a lateral decubitus position?
How about in children?
What happens to the pressure at the lumbar sac when the patient is seated?
Adult in lateral decubitus position: 100-180 mm H2O or 8-14 mm Hg
Child in lateral decubitus position: 30-60 mm H2O
When seated, there is about 2x increase in pressure
When does the CSF look hazy pink to red? At what number of RBCs/ mm3?
At 1,000-6,000 RBCs per mm3, CSF may be hazy pink to red in color
At at least 200 RBC per mm3 it may only be hazy or ground glass
What are the ways to discriminate between a traumatic tap in Subarachnoid hemorrhage, based on CSF results?
First, you need multiple samples
(1) A traumatic tap will have decreasing number of RBCs per sample
(2) A traumatic tap would have normal CSF pressure, in SAH pressure may be increased
(3) In traumatic tap, blood may clot or form fibrinous webs, this does not happen in SAH CSF
(4) in SAH, RBCs hemolyze within a few hours, it becomes pink-red (erythrochormia); if the tap is taken a t least one day after the bleed, then the supernatant fluid will already be xanthochromic
What can cause xanthochormia in the supernatant of CSF?
(1) Subarachnoid hemorrhage
(2) traumatic tap with a lot of venous blood ( more than 100,000 per mm3)
(3) severe jaundice
(4) diseases with increased CSF protein (at more than 150 mg/100 mL)
(5) hypercarotenimia
(6) hemoglobinemia
What is the usual ratio of WBC to RBC in a traumatic tap, when serum hematocrit is normal?
1 - 2 WBC per 1,000 RBC
What is Froin syndrome?
High CSF protein ( at least 1,000 mg/dL), deeply yellow CSF, and CSF that clots readily (because of presence of fibrinogen)
Seen in cases of block to CSF flow, such as in tumor, mass, infection)
What is the normal protein content of CSF in adults at the level of the lumbar spine? basal cistern? ventricles?
How about children?
Normal CSF Protein in Adults:
At lumbar subarachnoid space: 45- 50 mg/dL
At basal cistern: 10-25 mg/dL
At ventricles: 5-15 mg/ dL
In children, lower than adults, less than 20 mg/dL at lumbar subarachnoid spac
In hemorrhages, particularly into the ventricles or subarachnoid space, how does the protein level change relative to the number of RBCs?
CSF protein should increase by 1 mg per 1,000 RBCs,
However, in SAH, CSF protein may be even higher due to the irritating effect of hemolyzed RBCs to the leptomeninges
What is the major immunoglobulin in CSF?
How much of the CSF total protein does it comprise of?
What is its distribution relative to blood?
The major immunoglobulin in CSF is IgG
IgG comprise about 12% of the total CSF protein. (This may be higher in MS, neurosyphillis, SSPE, chronic viral meningitides)
Gamma globulin fraction in CSF is approx. 70% that of serum
What is the normal CSF glucose?
What is the normal proportion of CSF glucose to blood glucose levels?
How is this ratio affected by hypo or hyperglycemia?
Normal CSF glucose if 45-80 mg/dL
Normally, CSF glucose if 2/3 or 0.6 to 0.7 of blood glucose concentrations
In marked hyperglycemia, the ratio decreases to 0.5 to 0.6, in hypoglycemia, it increases to 0.85
What conditions can cause a false positive CALAS?
High titers of rheumatoid factor
High titers of antitreponemal antibodies
What conditions can cause false positive VDRL or RPR?
Collagen disease
Malaria
Yaws
What is the average osmolality of CSF? how does it compare to blood?
The average osmolality of CSF is 295 mOsm/L
This is similar to plasma
What isoenzyme of lactate dehydrogenase is present in the CSF of patients with bacterial meningitis but not aseptic or viral meningitis?
In what other condition can CSF LDH be elevated?
LDH Isoenzyme 4 and 5
LDH is also elevated in meningeal tumor infiltration, particularly in lymphoma.
(N.B. CEA is also elevated in meningeal tumor infiltration, but not in bacterial meningitis)
What pigments color the CSF in SAH? How can they be used to determine how old the hemorrhage is?
Oxygemoglobin- appears within several hours after the hemorrhage, becomes maximal in approx 36 hours, diminishes over a 7-9 day period.
Bilirubin- begins to appear in 2-3 days, increase in amount as oxygemoglobin decreases
Methemoglobin- appears when blood is loculated or encysted and isolated from the flow of CSF
At what GFR should IV contrast for CT scan be witheld to avoid inducing nephropathy?
Do not administer IV CT contrast for patients with GFR less than 30 ml/min/1.73 m2.
If GFR is between 30-60, may give CT contrast after hydration and discontinuation of nephrotoxic medications such as NSAIDS, cisplatin containing chemotherapy, aminoglycosides
How long after IV contrast for CT scan is given should you wait before repeating a contrast study?
Repeat infusion of IV contrast should be avoided if there is exposure to contrast in the last 72 hours
What are the possible complications of overexposure to radiation, ie in CT scans?
Alopecia, leukomalacia, neoplasia
Which atom’s signal does the MRI use to make images from?
Hydrogen. The MRI image is essentially a map of hydrogen content of tissue
What condition is a rare but severe possible complication of gadolinium?
How long after contrast administration can this occur?
Nephrogenic Systemic Fibrosis- this is a severe cutaneous sclerosing disease, it occurs mostly in patients with preexisting renal failure.
Kidney sclerosis may appear from several days to 2 months after procedure
How does fat appear in CT scan? MRI T1? T2?
Fat is black in the CT scan, White on MRI T1, Black on MRI T2
What marker in the MR spectroscopy indicate neuronal integrity?
In what conditions is it decreased?
N-acetylaspartate (NAA)
It is decreased in destructive lesions and in conditions where there is reduction in the density of neurons (ex. edema or glioma that increases distance between neurons)
